Board & Card Games Stack Exchange is a question and answer site for people who like playing board games, designing board games or modifying the rules of existing board games. It only takes a minute to sign up.

Do cards like Battlefield Forge add 2 mana each time it's tapped or is it just one of the two tapped mana options? Or can you choose between both at once vs one? And is the mana only there while it's tapped?

I believe your second question is answered by the other question you asked; mana is there until it is spent or until the end of the step/phase. The tapped status of the land has nothing to do with it.
– GendoIkariMar 15 '15 at 17:43

Whoops, hadn't looked at the other question - agreed, the two questions here are already answered.
– Cascabel♦Mar 15 '15 at 17:45

"is the mana only there while it's tapped?" From this question, I suspect you have a misunderstanding between the relationship between land and mana. A lot of new players think that a card that says "Add {R} to your mana pool" means "search your library for a Mountain card and put it on the battlefield" or "pretend you have a Mountain card in play which hangs around permanently" or something similar. But neither of these is how the card actually works.
– KevinMar 16 '15 at 17:13

1 Answer
1

You'll only get one mana, and like all mana, it'll be there until you spend it or until the end of the current step/phase. (There are a very small number of cards like Omnath, Locus of Mana in the game which change this, but they clearly, explicitly say so.)

Abilities are of the form "cost: effect". You pay the cost, and get the effect. In this case the cost is simply tapping the land. So you can choose one of those abilities to activate, then you'll have tapped the land, and you won't be able to activate the other anymore.